Can't help with the make of car; but wonder if Jim/bestie has documentary evidence that it indeed belongs to James Sheehan? Car-ownership, I believe was pretty much confined to the 'upper classes' even in the inter-war years, let alone before WWI. How likely wd. it have been for a publican to own a car? To me it seems more probable that the car's owner is one of the overcoat-&-cap-clad toffs standing in front of it, while landlord James surveys the scene, perhaps wishing the splendid vehicle were his.
Janet